1. Field
One or more embodiments of the present invention relate to a method of preparing carbon fiber from wood waste including an adhesive. More specifically, one or more embodiments of the present invention relate to a method of economically preparing high purity cellulose fiber from wood waste including an adhesive including urea resin and/or urea melamine resin, and a method or preparing high performance carbon fiber using the high purity cellulose fiber as a precursor fiber.
2. Description of the Related Art
Carbon fiber refers to a fiber, which is obtained by carbonizing of an organic fiber precursor, having 90% or higher carbon content. Carbon fiber may be classified as polyacrylonitrile(PAN)-based carbon fiber, pitch-based carbon fiber, and rayon-based carbon fiber, according to the type of the precursor. Due to the high performance properties such as high strength, light weight, and electric conductivity, carbon fiber is extensively used in manufacturing automobiles, ships, aircrafts, and spacecrafts.
The first carbon fiber was prepared by using cellulose fiber such as viscose rayon as a precursor material, but the physical properties and the carbonization yield were low. Hence, currently, most carbon fibers are produced by using an acrylic fiber which is prepared by using a PAN-based copolymer as a precursor. The PAN-based carbon fiber has excellent physical properties, but the price is high. To make carbon fiber be utilized generally in industries, carbon fiber of low price needs to be developed and provided. For this, carbon fiber may be prepared by using raw materials of low price or by recycling waste. From this point of view, a method of preparing carbon fiber by using wood as a raw material has been suggested.
In a representative method of preparing carbon fiber using natural wood, an attempt has been made to prepare carbon fiber by using lignin, which is generated in wood pulp process, as a precursor. However, as lignin itself is hard to be fiberized, carbon fiber was prepared by firstly preparing lignin composite fiber by mixing lignin with another synthetic polymer and fiberizing the mixture, and then carbonizing the lignin composite fiber. However, the carbon fiber prepared by the method is not commercially produced as the physical properties of the carbon fiber are very bad. On the other hand, as a method of preparing carbon fiber by using wood which has not undergone a purification procedure, a method of preparing cellulose fiber and carbon fiber wherein a spinning dope is prepared by dissolving wood power of a size of 80 mesh or less in phenol solvent and melt spinning is performed with the spinning dope was suggested (Ma, Xiaojun. et. al. Wood Sci. Technology, 44, 3-11, 2010). However, the method has not been commercialized as the organic solvent used in the method, such as phenol, is harmful to human body and the environment, and thus the use is restricted.
Preparing cellulose fiber by using wood waste and preparing carbon fiber by using the cellulose fiber as a precursor may provide a great economic advantage in the aspects of resources recycling and economic feasibility. Wood waste is very cheap, as it is discarded by burying or incinerating, and thus wood waste has very high potential to be used as a raw material for preparing cellulose fiber and carbon fiber at a low price. However, as wood waste includes not only hemi-cellulose included in wood as well as a great quantity of an adhesive such as urea resin and urea-melanin resin which has been used in wood processing, it is difficult to obtain high purity cellulose pulp, which enables to prepare high performance carbon fiber, by means of the conventional natural wood pulping process. For this reason, there is not yet a known method of preparing high purity cellulose pulp from wood waste and preparing carbon fiber by using the high purity cellulose pulp as a precursor.